首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   159576篇
  免费   16470篇
  国内免费   7746篇
电工技术   11022篇
技术理论   17篇
综合类   13307篇
化学工业   24970篇
金属工艺   8853篇
机械仪表   10271篇
建筑科学   12550篇
矿业工程   4469篇
能源动力   4894篇
轻工业   14936篇
水利工程   3209篇
石油天然气   7716篇
武器工业   1557篇
无线电   18158篇
一般工业技术   17565篇
冶金工业   6096篇
原子能技术   1908篇
自动化技术   22294篇
  2025年   53篇
  2024年   2967篇
  2023年   3283篇
  2022年   5529篇
  2021年   7208篇
  2020年   5730篇
  2019年   4738篇
  2018年   4658篇
  2017年   5333篇
  2016年   4776篇
  2015年   6746篇
  2014年   8429篇
  2013年   9741篇
  2012年   11159篇
  2011年   11923篇
  2010年   10930篇
  2009年   10330篇
  2008年   10181篇
  2007年   9346篇
  2006年   9017篇
  2005年   7161篇
  2004年   5118篇
  2003年   4291篇
  2002年   4439篇
  2001年   3784篇
  2000年   3220篇
  1999年   2950篇
  1998年   2169篇
  1997年   1729篇
  1996年   1574篇
  1995年   1187篇
  1994年   1012篇
  1993年   696篇
  1992年   598篇
  1991年   444篇
  1990年   310篇
  1989年   276篇
  1988年   174篇
  1987年   139篇
  1986年   106篇
  1985年   64篇
  1984年   46篇
  1983年   42篇
  1982年   42篇
  1981年   36篇
  1980年   48篇
  1979年   16篇
  1976年   4篇
  1959年   11篇
  1951年   11篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
湖南出土的楚汉丝织品,以马王堆一、三号汉墓所出为代表,其色彩反映了我国当时印染工艺技术所达到的高度水平,其纹饰则显示了鲜明的时代特征,表现了运动、气势和古拙的艺术风格,充满着神奇浪漫的色彩。  相似文献   
2.
This article deals with the kinetics of two-step anionic polymerization by way of a non-steady state method. Several molecular parameters can be evaluated using the formulae developed. A bimodal molecular weight distribution function for the resulting polymer is derived from the set of kinetic differential equations, which is in agreement with the experimental data reported.  相似文献   
3.
本文用计算机数字模拟方法研究了电活性分子多层Z型L-B膜修饰电极的循环伏安行为。计算了电极与修饰L-B膜分子第一层之间的电荷转移速度常数K_o,L-B膜分子层间的电荷转移速度常数k_i;对峰电位差△E_p及阳极峰面积Q的影响,以及在不同条件下各层分子的氧化态分数随扫描时间的变化。为研究和设计电活性分子修饰电极的实际体系提供了大量数据和信息。  相似文献   
4.
A distributed problem solving system can be characterized as a group of individual cooperating agents running to solve common problems. As dynamic application domains continue to grow in scale and complexity, it becomes more difficult to control the purposeful behavior of agents, especially when unexpected events may occur. This article presents an information and knowledge exchange framework to support distributed problem solving. From the application viewpoint the article concentrates on the stock trading domain; however, many presented solutions can be extended to other dynamic domains. It addresses two important issues: how individual agents should be interconnected so that their resources are efficiently used and their goals accomplished effectively; and how information and knowledge transfer should take place among the agents to allow them to respond successfully to user requests and unexpected external situations. The article introduces an architecture, the MASST system architecture, which supports dynamic information and knowledge exchange among the cooperating agents. The architecture uses a dynamic blackboard as an interagent communication paradigm to facilitate factual data, business rule, and command exchange between cooperating MASST agents. The critical components of the MASST architecture have been implemented and tested in the stock trading domain, and have proven to be a viable solution for distributed problem solving based on cooperating agents  相似文献   
5.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method.  相似文献   
6.
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry  相似文献   
7.
Two coupled-mode theories based on individual waveguide modes and compound system modes, respectively, are briefly reviewed with proper modification and new comments. The relation between these two theories is built and it is found that one theory is actually an efficient approximation of the other. Also, the reason why the results obtained with the first more accurate than those obtained with the second is found. The constraint on both approaches is shown  相似文献   
8.
袁颖曦 《模具制造》2007,7(12):79-81
列举了民营模具企业常见的几种泄密现象,并提出了防范措施。  相似文献   
9.
A new integrated magnetic full wave DC/DC power converter that provides flexible transformer design by incorporating an independent output inductor winding is introduced. The transformer is implemented on a traditional three-leg magnetic core. The inductor winding can be separately designed to control the output current ripple. The cross-sectional area of the inductor core leg can be reduced dramatically. The operation and performance of the proposed circuit are verified on a 100 W prototype converter.  相似文献   
10.
We demonstrate the first programmable group-delay module based on polarization switching. With a unique binary tuning mechanism, the device can generate any differential group delay value from -45 to +45 ps with a resolution of 1.40 ps, or any true-time-delay value from 0 to 45 ps with a resolution of 0.7 ps. The delay varying speeds for both applications are under 1 ms and can be as fast as 0.1 ms. We evaluate both the dynamic and static performances of the device while paying special attention to its dynamic figures of merit for polarization-mode dispersion emulation and compensation applications. Our experiment shows that the device exhibits a negligible transient-effect induced power penalty (<0.2 dB) in a 10-Gb/s nonreturn-to-zero system.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号